From the Magazine

Comet catcher

The comet 67P/Churyumov-Gerasimenko is tumbling into view, and Rosetta, a €1.3 billion flagship mission of the European Space Agency, is pursuing it. Launched in 2004, the spacecraft spent a decade chasing down the comet, and on 6 August, Rosetta will finally intercept it. There have been just a handful of comet missions, beginning in 1985 with Giotto's voyage to Halley's Comet, and each achieved its 15 minutes of fame through whipsaw flybys that lasted about that long. Rosetta, by contrast, will be the first to orbit a comet—no mean feat, given 67P's jumpy behavior and irregular gravity field. Rosetta is also the first spacecraft to accompany a comet during a full trip around the sun, and so it will watch as stores of ice thaw and sublimate, creating diffuse jets of gas that also blow out dust.